The present invention relates to a battery power control system, and more specifically, to a low-cost configuration and control method for a hybrid battery system which achieves both high energy density and high power density for use in an electric or hybrid electric motor drive system such as used in electrically propelled vehicles.
Propulsion systems for electric motor propelled vehicles ("electric vehicle" or EV) generally use rechargeable traction batteries to provide electric power for driving electric motors coupled in driving relationship to wheels of the vehicle. For example, U.S. Pat. No. 5,373,195 illustrates a system in which the traction batteries are connected to a direct current (DC) link, which link connects to a power control circuit such as a pulse width modulation (PWM) circuit for controlling power to a DC motor or to a frequency controlled inverter for controlling power to an alternating current (AC) motor. Hybrid electric vehicle (HEV) propulsion systems are constructed similarly to EV propulsion systems but also include internal combustion engines to drive on-board generators to supplement battery power.
In general, traction batteries for electric vehicles and hybridelectric vehicles represent a compromise between power density and energy density.